From 07e65ed88d31a36d49749cc1b02c1fef993faa28 Mon Sep 17 00:00:00 2001
From: Robert Rossmann <rr.rossmann@me.com>
Date: Thu, 23 Mar 2017 13:10:07 +0100
Subject: [PATCH] :racehorse: Epic performance boost for large files

Spectacularly improve rendering performance by only redrawing the
minimap at specific intervals instead of on each keystroke.
---
 lib/minimap.js | 53 ++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/lib/minimap.js b/lib/minimap.js
index 0d887257..0a390343 100644
--- a/lib/minimap.js
+++ b/lib/minimap.js
@@ -162,7 +162,6 @@ class Minimap {
      * @access private
      */
     this.configDevicePixelRatioRounding = null
-    /**
     /**
      * A boolean value to store whether this Minimap have been destroyed or not.
      *
@@ -179,6 +178,23 @@ class Minimap {
      */
     this.scrollPastEnd = false
 
+    /**
+     * An array of changes registered with textEditor.onDidChange() which have not yet been handled
+     *
+     * @type {Array}
+     * @access private
+     */
+    this.pendingChangeEvents = []
+
+    /**
+     * Timer reference which, once fired, will flush all the pending changes stored in
+     * this.pendingChangeEvents array.
+     *
+     * @type {Timer?}
+     * @access private
+     */
+    this.flushChangesTimer = null
+
     this.initializeDecorations()
 
     if (atom.views.getView(this.textEditor).getScrollTop != null) {
@@ -234,7 +250,7 @@ class Minimap {
     }))
 
     subs.add(this.textEditor.onDidChange((changes) => {
-      this.emitChanges(changes)
+      this.scheduleChanges(changes)
     }))
     subs.add(this.textEditor.onDidDestroy(() => { this.destroy() }))
 
@@ -260,6 +276,9 @@ class Minimap {
   destroy () {
     if (this.destroyed) { return }
 
+    clearTimeout(this.flushChangesTimer)
+    this.flushChangesTimer = null
+    this.pendingChangeEvents = []
     this.removeAllDecorations()
     this.subscriptions.dispose()
     this.subscriptions = null
@@ -276,6 +295,36 @@ class Minimap {
    */
   isDestroyed () { return this.destroyed }
 
+  /**
+   * Schedule changes from textEditor.onDidChange() to be handled at a later time
+   *
+   * @param  {Array} changes The changes to be scheduled
+   * @return void
+   * @access private
+   */
+  scheduleChanges (changes) {
+    this.pendingChangeEvents.push(...changes)
+
+    // If any changes happened within the timeout's delay, a timeout will already have been
+    // scheduled -> no need to schedule again
+    if (!this.flushChangesTimer) {
+      this.flushChangesTimer = setTimeout(() => { this.flushChanges() }, 1000)
+    }
+  }
+
+  /**
+   * Flush all changes which have been scheduled for later processing by this.scheduleChanges()
+   *
+   * @return void
+   * @access private
+   */
+  flushChanges () {
+    clearTimeout(this.flushChangesTimer)
+    this.flushChangesTimer = null
+    this.emitChanges(this.pendingChangeEvents)
+    this.pendingChangeEvents = []
+  }
+
   /**
    * Registers an event listener to the `did-change` event.
    *